1. Field of the Invention
The present invention relates to a device for data input and output and particularly to devices for data input and output which have multiple ports and are utilized in digital signal processing.
2. Prior Art
In the prior art there exist devices for data input and output which support digital processors; however, such prior art devices are generally single port devices. As a result, only one data source may be connected to the device and this presents a disadvantage. To overcome this disadvantage, the single port of prior art devices is multiplexed between a plurality of data sources; however, while such devices with multiplexing do provide for the connection of more than one data source to the device, they have an additional disadvantage in that they are slow.
Furthermore, since such multiplexed devices for data input and output still essentially use a single port, all of the data sources connected to the device must have the same characteristics or be of the same type. In other words, data sources which present serial data, parallel data or direct memory access may not be connected together to the same single port multiplexed data input and output device.
Also, prior art data input and output devices generally provide sequential operation. In particular, they either input or output, then process and then either input and output again. Processing in parallel with either input or output is not possible. As a result of this sequential operation of prior art devices, the through-put of such devices is inhibited and causes the processors which are connected to such prior art data input and output devices to wait and be slow.